This invention relates to low insertion force interface connectors and more particularly to apparatus for moving an array of electrical contacts into engagement with a second array of electrical contacts.
Fixture systems are generally known which include an actuator assembly for relatively moving a plurality of electrical test probes and a printed circuit board into electrical contact. Many of these devices employ an interchangeable test head carrying the electrical test probes. Due to the interchangeability of the test head it is necessary to provide an interface connector system for making electrical connection with the rest of the circuit board verifier as the interchangeable test head is inserted into the fixture system.
To this end, interchangeable test heads have also been provided with interface pins, one interface pin for each of the possible positions of the test probes on the interchangeable test head and an electrical connection is made between the probes and the corresponding interface pins. Additionally a set of interface contacts are provided in the fixture system and are electrically connected to a circuit board verifier. The interface pins and the interface contacts are arranged in mirror image arrays with one of the contacts in the array of interface contacts corresponding to each one of the interface pins in the array of interface pins. When the interchangeable test head is inserted into the fixture system, an electrical connection is made between each interface pin and the corresponding interface contact.
Various arrangements have been devised for bringing the interface pins and the interface contacts into engagement to thereby make electrical connection therebetween.
One type of prior art device is disclosed in applicant's copending application titled LOW INSERTION FORCE ELECTRICAL INTERFACE ASSEMBLY AND ACTUABLE INTERFACE ASSEMBLY THEREFOR, Ser. No. 148,537 filed May 9, 1980. In this device a low insertion force actuable interface assembly has a carrier mounting an array of electrical interface contacts. The axes of the contacts are substantially parallel to each other so that each contact extends to a free end. Carrier moving means is provided. The carrier moving means has at least one movable cam member guided for movement in a substantially straight line. The cam member has first and second cam portions. A first cam follower is connected to the carrier and is positioned for following the first and second cam portions for thereby guiding the movement of the carrier during movement of the cam member. The first cam part is connected to the carrier and the second cam part is connected for movement with the cam member. The movement of the cam member causes the cam follower to follow in sequence the first and second cam portions. The cam follower in following the first cam portion causes the carrier to move the contacts substantially parallel with the axes of the contacts. The second cam part forces the first cam part to move the carrier transverse to the axes of the contacts while the cam follower follows the second cam portion.
The guide means for guiding the cam member includes slots which provide a sliding interface between the guides and the cam bar. A disadvantage of such an arrangement is that considerable friction is generated between the sliding parts. Additionally, the cam follower is a shaft which slides along cam surfaces provided in the first and second cam portions. As a result, additional sliding friction is created. Additionally, a guide is provided for guiding the carrier in a vertical direction during the movement of the cam follower along the first cam portion. In the prior art device the guide is a vertically elongated slot in which the aforementioned shaft slides. As a result, additional sliding friction is created. The various components of sliding friction may add substantially to the force required to actuate the cam members and thus cause the two movements of the carrier.
Additionally a second cam member is provided interconnected with the first mentioned cam member so that both cam members move together in parallel. The second cam member also has first and second cam portions. An additional cam follower is provided for following the first and second cam portions of the second cam member similar to that described with reference to the first mentioned cam member. A side thrust camming arrangement forces the carrier to move in its transverse movement, not only transverse to the axes of the contacts but transverse to the direction of movement of the cam members. Since many contacts are involved, i.e., in the order of 8,000, the mating contacts will exert a substantial force on the contacts and thus on the carrier. As a result the carrier tends to tip unless adequate tolerances and precautions are used to prevent the tipping. The problem is compounded by present needs to increase the number of contacts to the order of 16,000 contacts.
Additionally the side thrust camming arrangement is provided between the cam member and the carrier. The side thrust camming arrangement includes two inclined surfaces which engage and slide in order to force the carrier to move in the direction transverse to the axes of the contacts. The inclined surfaces produce additional sliding friction.